interval function in oracle

Question

Query:

SELECT INTERVAL \'300\' month,
       INTERVAL \'54-2\' year to month,
       INTERVAL \' 11:12:10.1234567\' hour to second 
  FROM DUAL;

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Answer 1

INTERVAL is not a function it's a keyword that introduces an interval literal and such denotes a data type. Similar to what the literals DATE '2011-05-04' or TIMESTAMP '2011-05-04 17:18:19' are doing.

Details about interval literals
http://docs.oracle.com/cd/E11882_01/server.112/e41084/sql_elements003.htm#SQLRF00221
http://docs.oracle.com/cd/E11882_01/server.112/e41084/expressions009.htm#SQLRF52084

Details about the interval datatype:
http://docs.oracle.com/cd/E11882_01/server.112/e41084/sql_elements001.htm#i128552